1. Field of the Invention
This invention relates to submersible motors and is specifically concerned with an improving bearing assembly for an integral motor/propeller unit for water vehicles that provides an improved centering of the rotating assembly and an increase in the operating life of the bearing while enhancing the capability of the bearing assembly to survive shock loads.
2. Description of Prior Art
Integral motor/profiler units are known in the prior art. Such units are used either as surface vessels or for submersible vessels. Examples of integral motor/propeller units as a secondary drive unit for a submarine are disclosed U.S. Pat. No. 4,831,297 and in patent application U.S. Ser. No. 571,970 filed on Aug. 23, 1990, both developed owned by Westinghouse Electric Corporation. Generally, the bearings of these secondary drive units are lubricated by sea water which contains silt, and, shell particles, and other contaminants. The advanced design of the prior art of U.S. Pat. No. 4,831,297 involves a shroud having a water inlet and a water outlet. This unit is design to increase the thrust output for a given weight and size, while at the same time reducing the amount of cavitation generated due to the large unencumbered flow of water that the propeller of the device forces through the fluid-dynamically shaped shroud. Even though the integral motor/propeller unit of U.S. Pat. No. 4,831,297 represents a substantial advance in the art, several features of this design were improved upon by the unit disclosed in the aforesaid application bearing U.S. Ser. No. 571,970, in that this design provides a unit with more easy access to the bearings for their inspection and replacement.
The design of U.S. Ser. No. 571,970 has a bearing assembly which includes a thrust bearing and a radial bearing located between the hub of the propeller and the shaft, and includes an impeller mechanism which circulates the flow of lubricating and cooling water between the surfaces of the bearings.
In the integral motor/propeller units discussed hereinabove, the thrust and the radial bearings may have wear surfaces where one of the surfaces is either rubber or a phenolic material and the other bearing surface is metal. This type of bearing with the "soft-on-hard" bearing surfaces does not adequately control the centering of the rotating assembly in the stationary assembly as is required for submersible motor/propeller units because of the "soft" nature of the one beating surface. These types of bearings are also known as having a short operating life in view of the excessive wear of the soft material in the presence of the contaminants common in sea water.
This type of beating can only be used for applications with relatively low unit loads and is prone to failure if there is a loss of the lubricating fluid film on a decrease in the cooling water flow through the bearing assembly. The bearing assembly with "soft-on-hard" bearing surfaces can withstand relatively high levels of shock loading without sustaining any significant damage to the beating surfaces themselves, but, tends to permit large deflections of the rotating assembly during shock loading events that can make the rotating assembly prone to unacceptable levels of damage.
Previously, Westinghouse Electric Corporation had employed thrust and radial bearings for a bearing assembly of a submersible motor for a submersible vessel which had beating surfaces made of a relatively hard metal, for both beating surfaces, commonly referred to as "hard-on-hard" surfaces, as opposed to the beating surfaces being rubber or phenolic material contacting metal material, as discussed in the above examples of the prior art.
This type of bearing design with the "hard-on-hard" beating surfaces does provide better control of the centering of the rotating assembly and does increase the bearing operating life, but is not capable of withstanding high impact shock loads without significant damage that can render the rotating assembly inoperable.